Expanded (up to 24 or more LEDs) wiring for the LED Power Distribution Jr.

As stated on our
Board Layout page, the N8105 will allow
up to 4 series-wired LEDs on side
A of the board. This quantity is based on the assumption that an
18-volt power supply is used and the LEDs are of the white "family" (white,
incandescent, yellow-white, warm-white, sunny-white) which typically have device
voltages of 3.3 volts DC. The current source on side A takes 5-volts for normal
operation, leaving the remaining power supply voltage for the connected LEDs (4
LEDs times 3.3-volts = 13.2 volts).

We also show that an additional 4 LEDs
can be wired with resistors, directly to side B and be eitherseries groups or individual (parallel wired) LEDs.

However...

For side B (only) there
is an additional way LEDs can be connected that can greatlyexpand the board's capability (up to a total of 20 or
more LEDs). This is accomplished by connecting series groups to the
board with the series connections between the LEDs (daisy-chain wiring)
off board, then connecting the anode of the
first LED in the series group to the 'A' anode solder pad and the
last cathode in the group to the 'C' cathode solder pad.

Since there are 4 solder pad pairs, each
with resistor placement pads and cathode grounding bridge-pads on side B,
each solder pad pair can be a series group connection point. The actual quantity
of LEDs in the group is only limited by the voltage of the power source and the
combined device voltages of the LEDs in the group. Remember, in
series, you add the device voltages of the LEDs together and use that value when
calculating resistor requirements. If review of the series-wired calculations is
needed, it can be found here.

When using an 18-volt power supply:

Up to 5 white "family" LEDs can be in a series group (3.3 x 5
= 16.5-volts). If all 4 LED positions are used, that's 20 LEDs.

Up to 9 red LEDs (1.85 device voltage)
can be in a series group (1.85 x 9 = 16.65-volts). If all 4 LED positions are
used, that's 36 LEDs.

Other LED colors have different device
voltages so the exact quantity in a given series group may vary. DO NOT
mix colors of LEDs in a series group when using a resistor for current
control! Bad things can happen due to variations in the LED's internal
resistances.

LED colors CAN be mixed
in series groups when using the A side of the board, because
the current source IC senses each LED in the series group and provides 20ma to
each. Very clever indeed.

When using a 12-volt power supply:

Up to 3 white "family" LEDs can be in a series group (3.3 x 3
= 9.9-volts). If all 4 LED positions are used, that's 12 LEDs.

Up to 6 red LEDs (1.85 volt device voltage) can be in a series
group (1.85 x 6 = 11.1-volts). If all 4 LED positions are used, that's
24 LEDs.

Once again, DO NOT mix colors of LEDs in a
series group when using a resistor for current control!

Figures 1 shows a typical off-board wired series group. Details are noted by
a
red circled area and corresponding comments.
The corresponding numbers are described below:

1. Shows the anode solder pad for the connection of the first LED anode in
the series group.

2. Shows the
cathode solder pad for the connection of the last LED cathode in the series
group.

3. Shows the placement of a current limiting resistor on the resistor solder
pads for the group.

4. Shows the cathode grounding-bridge pads. Apply solder
to these 2 pads to bridge them together. This will complete the series group
connection to the board.

5. Shows bridging pads to connect on-board cathode
connections to anode connections. DO NOT apply solder the these
bridge connections when performing off-board series wiring.